1. Field of the Invention
The present invention relates to a connector, and particularly to a high speed connector having a controlled impedance.
2. Description of Related Art
With the development of communication and computer technology, high speed electrical connectors are more and more desired. There have already been several high speed electrical connectors available in the market, for example, Molex""s Very High Density Metric (VHDM) connectors (note: VHDM is a registered trademark of Teradyne, Inc.), and AMP""s Speedpac backplane connectors. One of the main problems of these high speed electrical connectors is the crosstalk in the connectors which deteriorates the quality of signal transmission seriously. It is a principle that the higher the speed is, the more serious the cross-talk problem becomes. It has been known by persons skilled in the art that matched impedance at interfaces of the connectors is critical to eliminate the cross-talk problem. A book entitled xe2x80x9cELECTRONIC CONNECTOR HANDBOOKxe2x80x9d, edited by Robert S. Mroczkowski, discloses in its chapter 12, pages 10-16 that allocating a number of pins as grounds in an open pin field connector is helpful to control the impedance of the connectors. Minimizing the distance between a signal pin and adjacent grounding pins improves electronic performance of the connector. Providing grounding pins around signal pins also reduces crosstalk. U.S. Pat. No. 5,713,764, assigned to Molex and issued on Feb. 3, 1998; U.S. Pat. No. 5,895,278, assigned to Thomas and Betts and issued on Apr. 20, 1999; U.S. Pat. No. 6,019,639, assigned to Molex and issued on Feb. 1, 2000; and U.S. Pat. No. 6,053,751, assigned to Thomas and Bitts and issued on Apr. 25, 2000 all disclose controlled impedance connectors for improving the problem of crosstalk of connectors having high speed transmission.
Accordingly, an objective of the present invention is to provide a high speed electrical connector with matched impedance so that crosstalk of the connector is significantly reduced.
In order to achieve the object set forth, an electrical connector includes a first housing member, a second housing member attached to the first housing member by a cap, a plurality of contacts and a plurality of grounding buses assembled to the second housing member and a plurality of printed substrates assembled to the first and second housing members. Each printed substrate has a first edge adjacent a front face of the first housing member, a perpendicular second edge received in a slot of the second housing member. The printed substrate has a plurality of couples of traces and a plurality of grounding coatings in on a first surface thereof and each grounding coating is located between two adjacent couples of traces. The printed substrate further has a row of first conductive pads adjacent the first edge and a row of second conductive pads adjacent the second edge and both rows are on the first surface. The first and the second conductive pads are electrically interconnected via the conductive traces. Each first conductive pad includes a first section connected to the conductive trace and a second section close to the first edge. The first section is slimmer than the second section for controlling the impedance of the route of the conductive pads and the conductive trace. The printed substrate has a grounding coating on an opposite second surface for controlling the impedance of the route of the trace and the conductive pads.